1. Field of the Invention
The present invention relates to a portable terminal which is equipped with a jack interface for connection to an audio device, and a method of recognizing an audio device in a portable terminal.
2. Description of the Related Art
Conventionally, portable terminals such as a note-type PC (personal computer), PDA (Personal Digital Assistant) and the like are equipped with a jack interface for connection to an audio device such as an external headphone, a microphone or the like.
For example, a portable terminal having a relatively large physical size such as a note-type PC can be equipped with a plurality of jack interfaces.
On the other hand, a small portable terminal such as PDA is generally equipped only with a single jack interface to enable connection only with a single audio device because the physical size limitations of the portable terminal make it difficult to include multiple jack interfaces.
In recent years, however, due to advances in multi-media functions and solution systems, even small portable terminals have been required to accommodate a plurality of audio devices,
To address this requirement, research has been focused on techniques for enabling portable terminals to be equipped with only a single jack interface, in order to maintain the small size of the terminal, and which is capable of recognizing the type of an audio device that is connected to this jack interface so that the portable terminal can accommodate a plurality of different types of audio devices.
By way of example, JP-A-11-162574 (hereinafter called “Patent Document 1”) discloses a technique for recognizing whether a plug of the audio device connected to a jack interface is a four-pole plug of AV or a three-pole plug of headphone.
Thus, the prior art disclosed in Patent Document 1 is capable of recognizing whether an audio device has a four-pole plug or three-pole plug.
However, since three-pole plugs are employed in a large number of types of audio devices, including a headphone, an earphone/microphone, and a stereo microphone, these audio devices cannot be strictly recognized from each other.
For this reason, the prior art disclosed in Patent Document 1 fails to adequately address the requirement that a portable terminal be able to accommodate a plurality of audio devices while maintaining its small size.